The present invention relates to radio frequency (RF) power amplifiers (PA) module.
Portable devices such as laptop personal computers (PC), Personal Digital Assistant (PDA) and cellular phones with wireless communication capability are being developed in ever decreasing size for convenience of use. Correspondingly, the electrical components thereof must also decrease in size while still providing effective radio transmission performance. However, the substantially high transmission power associated with RF communication increases the difficulty of miniaturization of the transmission components.
A major component of the wireless communication device is the radio frequency PA. The PA is conventionally in the form of a semiconductor integrated circuit (IC) chip or die in which signal amplification is effected with substantial power. The amplifier chip is interconnected in a circuit with certain off-chip components such as inductors, capacitors, resistors, and transmission lines used for controlling operation of the amplifier chip and providing impedance matching of the input and output RF signals. The amplifier chip and associated components are typically assembled on a printed circuit board (PCB) in which the components are interconnected by layers printed metal circuits and layers of dielectric substrates.
One consideration for wireless devices is to properly control the quality and power level of the amplified RF signals to be transmitted. In particular for high data rate wireless communications, the amplification of RF signals is required to be linear over a wide signal power range and over a given frequency range. Preferably the amplification is reduced or increased according to input RF signal, transmittance range and data rate so that power consumption can be optimized.
Other considerations in using wireless devices include good grounding and RF signal isolation. A power amplifier typically has high current flowing through the circuit. A non-zero impedance in the circuit can easily induce a voltage, potentially injecting unwanted noise into the RF system. Poor circuit board grounding can thus cause unintended feedback and oscillations. The ground current paths and the current handling capability of components have to be considered carefully. Since RF circuits operate at high power and high signal frequencies, electromagnetic radiation created can interfere with other components of the wireless communication device, or with other electronic devices.
Another consideration in the miniaturization of RF amplifier circuits is the required impedance matching for the input and output RF signals of the amplifier. Input and output impedance matching circuits typically include capacitors, resistors, and inductors in associated transmission lines or micro strips for the RF signals into and out of the amplifier chip. However, these impedance matching circuits may require specifically tailored off-chip components located remotely from the amplifier IC chip. Accordingly, the application circuitry must include many electrical input and output terminals or bonding Pins to which the corresponding portions of the off-chip impedance matching circuits are separately joined. This increases the difficulty of assembly and required size of the associated components, and affects the overall manufacturability of the portable devices.